Fellow liberal here. Along with liberal civil rights, economic policy, comes a belief in liberal freedom: The freedom to speak as we wish, the freedom to keep and bear arms. And as a liberal, I have a liberal view of "keep and bear arms". By keep and bear, I interpret that as "possess, buy, sell, rent, use, and enjoy for any sake or no sake", and by arms I mean "anything short of a full-blown nuclear weapon". 40mm grenade launcher? Hey, what you do and have isn't any of my business, more power to you! 20mm Lahti anti-tank rifle? Who am I to say you can't own and enjoy one in the privacy of your own home or at a gun range?
If we believe in rights for minorities, we must also believe in rights for everyone. All of them, not just the ones we can sell.
I wish more liberals felt like I did.